Xerographic process



Sept. 14, 1965 F. G. LUDWIG 3,206,307

XEROGRAPHIC PROCESS Filed Aug. 1e, 1965 ATTORNEYS United States Patent O 3,206,307 XEROGRAPHIC PROCESS Frederic G. Ludwig, S. Pease Road, Woodbridge, Conn. Filed Aug. 16, 1963, Ser. No. 302,584 1 Claim. (Cl. 96-1) This invention relates to the electric photography copying art in general, and in particular to improvements in the copy paper employed with such machines which are commonly referred to as xerographic type copiers.

In machines of this type the image of the original document is ordinarily transferred in electrostatic charged form onto an intermediate surface. The intermediate surface is subsequently treated with a fusible ink-like powder material which adheres to the charged portions of the surface corresponding to the image of the original document. The fusible material is thereafter transferred to the surface of the copy paper whereupon the copy paper is subjected to a heated environment to permanently fuse the material in the form of the original document onto the copy paper. Because this process, commonly known as the xerographic copying process, requires that the copy paper be subjected to a relatively high fusing temperature, la fairly substantial heavyweight paper is used to prevent warping and buckling of the paper within the machine. Twenty pound paper stock is normally required for satisfactory performance. Such paper is not only expensive, but relatively bulky requiring a high degree of tile storage space in contrast to copies made on thin sheets of paper by other methods wherein such thin paper is compatible with the copying process.

In xerographic copiers of the type employing the sequential feeding of individual sheets of copy paper, accurate feed registration and timing of the copy paper relative to the timing of the latent image on the intermediate member is obviously required for satisfactory copy quality. Again, obtaining the required feeding accuracy of the copy paper necessitates a relatively thick paper stock because thin paper stock can not be handled by the copy machines feed mechanism with any degree of registration accuracy.

Another reason that fairly heavy paper stock is required is because as the paper approaches the image carrying surface it is given an opposite electrical charge from that of the image carrying surface so that the paper and surface attract each other like a magnet. If the copy paper is not perfectly iiat as it transfers to the image carrying surface wrinkles and improper contact therewith occur.

Accordingly, an object of the invention is to provide a novel copy paper stock material of a laminated form wherein during its passage through the machine, it presents a rigid, relatively thick sheet, which may be subsequently separated into a thin sheet bearing the copied image and wherein the backing or carrier sheet may be discarded or reused as desired.

A feature of applicants invention is that it facilitates the use of the xerographic copying technique for production of extremely thin copies that require greatly reduced storage space and which may also be used as the master for subsequent copying by alternate copying processes, such as the diazo process, to lower the cost of additional copies.

While copy machines which feed individual sheets of copy paper have the added difliculty of registration accuracy with thin paper stock, it should be appreciated that the present invention may be used to similar advantage on copy machines employing a continuous web of copy paper.

These and other objects and advantages of the invention will become apparent, and the invention will be 3,206,307 Patented Sept. 14, 1965 ICC fully understood from the following description and drawings, in which:

FIGURE l is an internal perspective view of a typical copier of the type described;

FIGURE 2 is a schematic cross-sectional view showing the six essential steps employed in the copying machine of FIG. l;

FIGURE 3 is a perspective View of a single sheet of copying paper in accordance with the invention as employed in the machine of FIG. 1; and

FIGURES 4 to 8 inclusive, are exploded cross-sectional views taken along section lines 4-8 to 4-8 of FIG. 3.

Referring to the drawings in particular, a copying machine shown generally at 10 includes an original document 12 placed face down thereon whose downwardly facing image is scanned by a suitable scanning means 14. The scanned image is progressively transferred to the surface of a rotating intermediate or drum member 16 which has been previously electrostatically charged by a mechanism shown generally at 18. Thereafter, the latent electrostatic image on the rotating drum 16 corresponding to the document image is subjected to Ia developing mechanism shown generally at 20. The mechanism 20 includes an endless conveyer means .22 which disperses the fusible material 24 over the surface of the drum. The fusible material adheres to the areas of the drum corresponding to the image on the original document 12. Thereafter, feeding means (not shown) acting in cooperation with a pair of register rollers 30 sequential-ly advance individual sheets of copy paper 28 from a supply stack of paper 26. The feeding of each of the individual sheets 28 is in timed and oriented relation to the image on the surface of the rotating drum 16. Each sheet 28 passes between the transfer mechanism 32 and the surface of the drum whereby the image from the drum is transposed to thevsurface of the paper. The copy paper now 28 containing the fusible material thereon in the pattern of the image on the original document is subsequently conveyed by the horizonatl transport system 34 below a fuser means 36. The heated material 24 is thus permanently joined with the copy paper 28.

The fuser means 36 raises the temperature of the copy paper and material thereon to a relatively high temperature. Accordingly, machines of this general type require a relatively thick piece of sheet stock as the copy paper to prevent undue warping and buckling in this high temperature environment. In addition, because the entire copying process involves the use of an intermediate image transfer member such as the drum 16, it is necessary that an accurate preregistered and timed feeding of the copy paper be maintained relative to the image scanning means 14 operating on the document. This may be con trasted with the usual photographic copying means wherein the copy material is placed in direct contact with the document and therefore no accurate feeding of the sheet is required.

After the image has been fused to the copy paper 26 it travels upwardly through the feed rollers and transport system 40 to be collected in the delivery hopper 41. Additional means shown generally at 38 are provided to clean the rotating drum 16 and remove all residuary fusible material therefrom prior to re-charging by the means 18. A more detailed description of the basic copying mechanism is not believed required for the purposes of under; standing the present invention. However, a machine of this general type is described in United States letters Patent No. 3,062,095 and reference may be made thereto for a fuller comprehension of the operating details thereof.

Referring to FIGS. 3 to 8 inclusive, various novel laminated copy paper arrangements are disclosed employing alternate carrier sheet and manifold sheet materials. Each of FIGS. 4 to 8 show a representative copy sheet 28 in exploded cross-section wherein the laminations are shown in separated positions.

In FIG. 4, the novel copy paper sheet stock includes a thin manifold layer 42 secured by a pressure sensitive adhesive layer 44 to a backing or carrier sheet 46. The manifold sheet 42 is preferably made of thin paper stock in the order of .002 inch thickness. Paper in accordance with this embodiment is placed in the copy machine of FIG. 1 with the manifold sheet 42 facing upward. After completion of the copying process, the manifold sheet 42 is separated from the backing sheet 46 (by means not shown) to produce an extremely thin xerographically copied document unobtainable from such a machine prior to applicants invention. After separation of the sheet 42 it may be used as a diazo master for subsequent reproduction by an alternate and less expensive copy technique. Furthermore, the thin copy 42 saves considerable ling space in View of tis considerably decreased bulk.

FIG. 5 shows an alternate manifold sheet designated 48 of tracing paper which exhibits more durability than the manifold sheet 42 of FIG. 4. In view of the higher transparency of the sheet 48 it is possible to run the subsequent diazo duplicating machine at a faster production rate than would be possible with a lower transparency sheet such as 42.

FIG. 6, shows another embodiment of copy paper wherein the manifold sheet 50 is formed of thin rag stock paper secured by adhesive layer 44 to a similar backing sheet 46. Again, after copying and separation of the manifold sheet 50 from the backing sheet a high quality low bulk copy is produced which is particularly suitable for permanent records.

FIG. 7, employs a manifold sheet 52 preferably of etched or matt surface plastic secured by means 44 to a black paper backing sheet 54. Again, after separation of the sheet 52 from the carrier sheet, a high quality fast running diazo master is obtained. This embodiment inclndes the further advantage that the uppermost sheet 52 is reusable if desired by the removal of the image therefrom with a suitable solvent.

FIG. 8 is similar to the embodiment of FIG. 7 but employs a clear plastic material for the image receiving manifold sheet 56 which is secured by means 44 to a black backing sheet 54. In this embodiment, the image is deposited upon the transparent sheet 56 which may be used for projection purposes.

Thus, it can be seen how applicants novel use of a multi-layer copy paper sheet capable of subsequent separation into individual layers has resulted in a means for producing a xerographic copy upon an extremely thin sheet of paper. Hithertofore, such result was totally unobtainable from this type copying machine due to their adverse heat environment and the need for the accurate feeding of a sheet therethrough.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

I claim:

The method of producing a heat fusible image on a thin image receiving sheet which comprises attaching the image receiving sheet to a heavy carrier sheet producing an electrostatic charge on a xerographic surface, exposing said xerographic surface to a light image, applying a fusible toner powder to said surface to develop the image thereon, transferring the powder image to said image receiving sheet, fusing the image on said image receiving sheet and, subsequent to the fusion of said image, separating the image receiving sheet and the carrier sheet.

References Cited by the Examiner UNITED STATES PATENTS 1,951,620 3/34 MacLaurin 161-406 X 2,221,776 ll/40 Carlson 95-l.7 X 2,661,289 l2/53 Mayo et al.

3,062,110 1l/62 Shepardson et al. l6l-406 X 3,075,446 l/63 Horne 161-406 X EVON C. BLUNK, Primary Examiner. 

